Preparation of highly porous SiC via ceramic precursor conversion and evaluation of its thermal insulation performance

ABSTRACT

Porous SiC ceramics were prepared based on precursor conversion method using liquid hyperbranched polycarbosilane (LHBPCS) as the preceramic polymer and expandable microsphere (EMS) as the pore foaming agent. By optimising the content of free radical initiator, the cross-linking process of LHBPCS is synchronised with the foaming process of EMS. The addition of EMS had no serious effect on the cross-linking reaction mechanism and rate of LHBPCS, and the cross-linking of LHBPCS did not significantly confine the foaming of EMS. After 1000°C pyrolysis, EMS decomposed, but its spherical shape with sizes of 20–30 μm homogeneously embedded in the pyrolysed LHBPCS. As a result, a highly porous SiC foam with density of 0.211 g cm^–3 and porosity of 91.2% was obtained and its thermal conductivity at room temperature was as low as 0.05 W (m K)^–1. In addition, with increasing test temperature, its thermal conductivity increased slowly, indicating a good thermal insulation property.

KEYWORDS:

• Porous SiC
• precursor conversion
• low density
• low thermal conductivity

Acknowledgements

This work was supported by the Special Foundation of President of the Chinese Academy of Sciences (Grant No. [2018] NO.1), and Research & Development of Nuclear Materials and Service Safety Assurance Technology (Grant No. ZDRW-CN-2017-1).

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by the Special Foundation of President of the Chinese Academy of Sciences [grant number [2018] NO.1], and Research & Development of Nuclear Materials and Service Safety Assurance Technology [grant number ZDRW-CN-2017-1].